"This committee is known for being partisan and political. They did not consult or co-operate with the Republicans on the committee," Dana Perino, White House press secretary, said.

She called the report a "partisan attempt to overshadow positive developments in Iraq".

Jack Burkman, a Republican strategist, argues the figure released in Tuesday's report is deceptively high.

He said: "Our military, much more so than others throughout the world, is outsourced, so if you want to talk money and finance, it's just not as bad as people think."

The JEC estimate assumes the number of US troops in Iraq will reduce over time but a large-scale US force will be retained there.

Pull-out vote

The committee also estimated the cost of repair and refitting military equipment, the money needed to keep soldiers in the ranks and the costs to the US domestic economy of deploying US army reserve units.

The house of representatives will vote this week on another effort by Democrats to set a deadline for the withdrawal of troops from Iraq, making it a condition for providing another $50bn for the war.

The proposal would require the withdrawal or re-deployment of most troops in Iraq to begin immediately, with a goal of ending combat operations within a year.

George Bush, the US president, has repeatedly resisted attempts to force him to accept timelines for pulling troops out of Iraq.

If Bush vetoes the bill, "then the president won't get his $50bn", Reid said.